Highly diastereodifferentiating and regioselective [2+2]-photoreactions using methoxyaromatic menthyl cyclohexenone carboxylates

Chiral Cyclohexenone 1a is irradiated in the presence of various alkenes to yield highly diastereodifferentiating (1S,6S) configurated oxobicyclo[4.2.0]octanes. For increasing the de of the reaction, we designed a new chiral auxiliary owing a methoxynaphthylmenthyl moiety b: cyclohexenone carboxylate 1b. Irradiation of 1b in the presence of various alkenes shows high diastereo- and regioselectivity, yielding (1S,6S)-bicyclo[4.2.0]octan-2-ones with a de of up to 96%.